Abstract
Seeds of 22 plant species including host plants for Erwinia aroideae were used. Immediately after inoculation of E. aroideae to air-dried soil, surface-sterilized seeds were sown in this moist soil, and grown under field conditions. The seeds germinated within a week, and during this period the introduced pathogen predominated in this soil. From thirty-two days after seeding, rhizosphere populations of the growing plants were examined periodically by dilution plating and immunofluorescent staining.
E. aroideae was recovered from the rhizosphere of only three plants, i.e. chinese cabbage, cucumber and morning-glory, in 3 cases of 52 tested, using the dilution plate method (Table 2). Immuofluorescent staining revealed survival of E. aroideae in the rhizospheres of chinese cabbage, radish, wheat, oat, red bean, tomato, cucumber, sponge-gourd, and morning-glory (Table 2 and Plate). On the contrary E. aroideae was detected consistently in the control soil during the experimental period by dilution plating using modified Drigalski's medium (Table 1).
These results suggest that growing plants, including host plant, at least in early stages of growth can not effectively support the growth of E. aroideae and perhaps hasten the death of the pathogen through the intense microbial competition around the roots.
